title: Stretch-shorten cycle compared with isometric preload: contributions to enhanced muscular performance.
abstract: To isolate any difference muscular contraction history may have on concentric work output, 40 trained male subjects performed three separate isokinetic concentric squats that involved differing contraction histories, 1) a concentric-only (CO) squat, 2) a concentric squat preceded by an isometric preload (IS), and 3) a stretch-shorten cycle (SSC) squat. Over the first 300 ms of the concentric movement, work output for both the SSC and IS conditions was significantly greater (154.8 +/- 39.8 and 147.9 +/- 34.7 J, respectively; P < 0.001) compared with the CO squat (129.7 +/- 34.4 J). In addition, work output after the SSC test over the first 300 ms was also significantly larger than that for the corresponding period after the IS protocol (P < 0.05). There was no difference in normalized, integrated electromyogram among any of the conditions. It was concluded that concentric performance enhancement derived from a preceding stretch of the muscle-tendon complex was largely due to the attainment of a higher active muscle state before the start of the concentric movement. However, it was also hypothesized that contractile element potentiation was a significant contributor to stretch-induced muscular performance under these conditions.
authors.affiliation: School of Exercise Science and Sports Management, Southern Cross University, Lismore, New South Wales, Australia. awalshe@scu.edu.au
authors.forename: A D
authors.initials: AD
authors.lastname: Walshe
authors.forename: G J
authors.initials: GJ
authors.lastname: Wilson
authors.forename: G J
authors.initials: GJ
authors.lastname: Ettema
mesh_terms: D000328:Adult; D004576:Electromyography; D004594:Electrophysiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D015203:Reproducibility of Results; D014891:Weight Lifting / Q000502:physiology